Shulou(Shulou.com)06/01 Report--

This article shows you what the role of red glue on pcb is, the content is concise and easy to understand, it can definitely brighten your eyes. I hope you can get something through the detailed introduction of this article.

Red gum is a kind of polyolefin compound, which is different from tin paste in that it solidifies after being heated and its freezing point temperature is 150 ℃. At this time, red glue begins to change from paste body to solid body directly. Red gum belongs to SMT material. The following will lead you to understand what is the red glue on the pcb board, what is the role of the red glue on the pcb, the role of the red glue in the SMT patch processing and the standard process of the PCB red glue.

What is the red glue on the pcb board?

In the mixed process of SMT and DIP, in order to avoid the secondary passing of one-sided reflow soldering and one-time wave soldering, the red glue is applied on the center spot of the chip element on the wave soldering surface of PCB, and the solder paste printing process can be saved.

SMT "red glue" process? In fact, its correct name should be SMT "dispensing" process, because most of the glue is red, so it is commonly known as "red glue". In fact, there is also yellow glue, which is the same reason that we often call the "solder mask" on the surface of the circuit board "green paint".

We can find that there is a red gelatinous object in the middle of these small parts, such as resistance and capacitance. This is red glue. This red gel process was developed because there were still many electronic components that could not be immediately transferred from the original plug-in (DIP) package to the SMD package.

There are half DIP parts and the other half SMD parts on a circuit board. How do you place some parts so that they can be welded to the board automatically? In general, all DIP and SMD parts are designed on the same side of the circuit board, SMD parts are printed with solder paste and soldered back to the furnace, while the remaining DIP parts are exposed on the other side of the circuit board, so you can use wave soldering furnace process to weld all DIP pins at one time. So at the beginning, we all need two welding processes to weld all the components well.

In order to save the layout space of PCB, we hope to put more components into it. Therefore, SMT devices are also needed on the bottom surface. At this time, in order to glue the parts to the circuit board, and then let the circuit board pass through the wave soldering furnace, so that the parts can be tinned and bonded with the solder pad on the circuit board, without falling into the hot wave soldering furnace.

In order to reduce the technological process, we hope to complete the welding at one time. Through-hole reflow soldering can be used, but many of the plug-in devices we choose can not withstand the high temperature environment of reflow soldering. Therefore, through-hole reflow soldering can not be used. Therefore, only the mass products of some large companies may consider through-hole reflow soldering, because some high-cost plug-in devices that can withstand high temperatures can be purchased. The advantage of PCB circuit board proofing is that the time is short, the quality is high, the price is cheap, and the PCB board proofed has no missed soldering, so it uses through-hole reflow soldering.

And the general SMD parts have been designed to withstand reflow soldering temperature, reflow soldering temperature is higher than the wave soldering temperature, so SMD devices even if soaked in the wave soldering furnace for a short period of time will not have a problem, but printing solder paste is no way to let SMD over the wave soldering furnace, because the temperature of the solder furnace must be higher than the melting point of solder paste, so SMD parts will fall into the solder furnace because of solder paste melting.

So we need to fix the SMD device first, so we use red glue.

What is the function of red glue on pcb?

1. Red glue generally plays a fixed and auxiliary role. Solder is the real welding effect.

2. Prevent components from falling off in wave soldering (wave soldering process). When using wave soldering, the components are fixed on the PCB in order to prevent the components from falling when the PCB passes through the solder slot.

3. Prevent the other side components from falling off in reflow soldering (double-sided reflow soldering process). In the double-sided reflow soldering process, in order to prevent the large devices on the welded side from falling off due to the melting of the solder, it is necessary to have SMT adhesive.

4. Prevent the displacement and standing of components (reflow soldering process, pre-coating process). It is used in reflow soldering process and pre-coating process to prevent displacement and vertical plate during mounting.

5. Marking (wave soldering, reflow soldering, pre-coating). In addition, printed boards and components are marked with patch glue when they are changed in batches.

What is the function of red gum in pcb patch processing?

Patch processing adhesive, that is, patch processing red glue, is usually red (also yellow or white) paste evenly distributed with adhesives such as hardeners, pigments, solvents, etc., which are mainly used to fix patch processing components on the printed board and are generally distributed by dispensing or steel screen printing. After affixing the components, put them into the oven or reflow furnace to heat and harden.

Patch processing patch adhesive is its curing after heating, patch processing solidification temperature is generally 150 degrees, and then heating will not dissolve, that is to say, the thermal hardening process of patch processing is irreversible. The processing effect of the patch will vary according to the thermal curing conditions, the connectors, the equipment used and the operating environment. When in use, the patch adhesive should be selected according to the assembly process of the printed circuit board.

Patch processing red glue is a chemical compound, mainly composed of polymer materials. Patch processing fillers, curing agents, other auxiliaries, etc. Patch processing red glue has viscosity fluidity, temperature characteristics, wetting properties and so on. According to this characteristic of patch processing red glue, the purpose of using red glue in production is to make the parts stick firmly to the surface of PCB to prevent it from falling.

Patch processing red glue is a pure consumption material, not a necessary process product. now, with the continuous improvement of surface mount design and technology, through-hole reflow soldering and double-sided reflow soldering have been realized. there is a trend that the placement process of patch processing adhesive is less and less.

Standard process of SMT red gum

The standard production process of SMT red glue is as follows: screen printing → (dispensing) → mounting → (curing) → reflow soldering → cleaning → testing → repair → completion.

1. Screen printing: its function is to print solder paste (solder paste) or red glue (patch glue) to the pad of PCB circuit board to prepare for the welding of components. The equipment used is the screen printing machine (screen printing machine), which is located at the front end of the SMT process production line.

2, dispensing: it is to point the red glue to the fixed position of the PCB, and its main function is to fix the components on the PCB board. The equipment used is the dispensing machine, which is located at the front end of the SMT production line or behind the testing equipment.

3. Mounting: its function is to accurately install the surface mount components to the fixed position of the PCB. The equipment used is the placement machine, which is located behind the screen printing machine in the SMT production line.

4. Curing: its function is to melt the red glue (patch glue) so that the surface mount components are firmly bonded to the PCB board. The equipment used is a curing furnace, which is located behind the placement machine in the SMT production line.

5. Reflow soldering: its function is to melt the solder paste (solder paste) and make the surface mount components firmly bonded to the PCB board. The equipment used is a reflow furnace, which is located behind the placement machine in the SMT production line.

6. Cleaning: its function is to remove the harmful welding residues such as flux on the assembled PCB board. The equipment used is a cleaning machine, the position can be not fixed, can be online, can not be online.

7. Inspection: its function is to test the welding quality and assembly quality of the assembled PCB board. The equipment used are magnifying glass, microscope, on-line tester (ICT), flying needle tester, automatic optical inspection (AOI), X-RAY testing system, function tester and so on. The location can be arranged in the appropriate place of the production line according to the need of inspection.

8. Repair: its function is to rework the PCB board that is detected to be out of order. The main tools used are hot air gun, soldering iron, repair workstation and so on. The configuration is anywhere in the production line.

The above content is what is the function of red glue on pcb? have you learned the knowledge or skills? If you want to learn more skills or enrich your knowledge reserve, you are welcome to follow the industry information channel.

Welcome to subscribe "Shulou Technology Information " to get latest news, interesting things and hot topics in the IT industry, and controls the hottest and latest Internet news, technology news and IT industry trends.